Process for producing jacketed bodies



H. A. SALLER PROCESS FOR PRODUCING JACKETED BODIES Jan. 21, 1958 Filed Dec. 1, 1952 FIE- 3 I a l? ffa I PIE. 5

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Sal/er 2,820,751 rnocnss Fun PRODUCING JACKETED BODIES Henry A. Stiller, Columbus, Ohio, assignor to the United States of America as represented by the United States Atomic Energy Commission Application December 1, 1952, Serial No. 323,348

9 Claims. (Cl. 204- 1542) This invention relates to the provision of a jacket or cover for a metal core. More specifically, it relates to a process for encasing a metallic memberusable with a neutronic reactor.

An object of the present invention is toprovide a method for jacketing a metallic core containing a material fissionable by neutrons of thermal energy, such as uranium, so that the jacket will be tight and completely bonded to the core. Thus the core will be protected against cor rosion, the heat of fission will efliciently be conducted away through the jacket, and the jacket will retain the fission fragments coming from the core. If the fissionable material is U -enriched uranium, the core will also contain aluminum or zirconium alloyed with the uranium. With an aluminum-uranium core an aluminum jacket will be used, and with a zirconium-uranium core a zirconium jacket or a tin-zirconium jacket will be employed.-

I Another object is to provide a'method; of encasing a control member employed with a neutronic reactor. The control member may be formed of gadolinium oxide and titanium, and in this instance the jacket will be formed of titanium.

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. 2 ment of the process. of the present invention is carried out;

Fig. 8 is a vertical sectional view taken on the line 88 of Fig. 7; Fig. 9 is a perspective view of a frame that is employed in the process of the third embodiment; and

Fig. 10 is a perspective View of a modified form of frame used as part of a fuel-element jacket in the third embodiment.

Wherever a uranium alloy is employed in the modifications hereinafter mentioned, it is to be understood that the uranium in the alloy is enriched so as to contain 93% U and a balance of other isotopes. In utilizing the invention for fuel elements of other nuclear reactors, the degree of enrichment can be varied.

In the modification illustrated in Figs. 1, 2, and'3, a

- fuel-element core 10 is formed of an alloy composedof 3 to 40% uranium and the balance substantially aluminum. The fuel-element core is placed in a large opening 11 in an aluminum frame 12, which may be formed by a the cutting out of a large central section from a suitable bar. The opening 11 fits the fuel-element core 10 relatively closely. The thickness of the frame 12 is substantially that of the fuel-element core 10. An aluminum sheet 13 is wrapped about the assembled fuel-elementcore 10 and frame 12 so that opposedportions 13a and .A further object is to provide a method of applying a cation of Fermi and Szilard, Serial No.- 568,904, filed-- December 19, 1944, now Patent No. 2,708,656, issued May 17, 1955. For further information on reactors that I,

can utilize fuel elements disclosed in the present applica-' tiou, reference is made to copending application of Zinn, Serial No. 721,108, filed January 8, 1947,and the copending, application of Eugene P. Wiguer,=Seria1 No. 314,595, filed October 14, 1952.

,Other objects will become apparent from cation and the drawings, in which: a

Fig. 1 is a plan view, with portions cut away and-in section,of one form ofassembly upon which aprocess of the present invention is performed; 7

. Fig. 2 is a vertical: sectional view taken on the line 2-2 of Fig.- 1; i

Fig. 3 is a vertical sectional view similar to Fig. 2

.Fig. 6 isv a vertical sectional view taken .,on the line 6-6 of Fig. 5;

Fig. 7 is a plan view, with portions cut away, of still another formof assembly upon which a third embodi-' the specifi- 13b of the sheet lie at opposite faces of the frame and the fuel-element core and edges of the sheet portions 13a and 13b are joined in a folded seam 14. The sheet, frame, and fuel-element core are rolled at a suitable elevated temperature so that the structure of Fig. 3 is produced in which both parts'of the sheet are to the frame and to the fuel-element core and the frame bonded and the fuel-element core are bonded to one another. Now the portions of the sheet 13 protruding beyond the edges of the frame 12 (indicated in dotted lines in Fig. 3) are preferably trimmed ofi.

If the sheet portions 13a and 13b are of insufiicie'nt thickness after rolling, another similar aluminum sheet 15 is applied thereover as shown in Fig. 4 and the edges are joined in a'folded seam 16. Rolling is again performed at a suitable elevated temperature. The sheet 15 becomes bonded to the sheet portions 13a and 13b, and thus a-thicker aluminum covering is provided on the fuel element. Now the portions of the sheet 15 protruding beyond the frame 12 are preferably trimmed oif.

' The fuel-element core 10, which is formed by casting, is preferably worked by forging or rolling at an elevated temperature before it is assembled with the frame 12 and the cover 13. This facilitates the formation of bonds of the fuel element core with the cover and the frame.

If the fuel element has a relatively high percentage of uranium, it is advantageous to form the fuel element by chill-casting andworking.

vIn the modification illustrated in Figs. 5 and 6, a fuel-' element core 17 is formed of an alloy composed of 3 to 14% uranium and the balance substantially zirconium. The fuel-element core 17 is placed in a large opening 18 in a'zirconium frame 19, which may be formed by the cutting out of a large central section from a suitable bar.

' The fuel-element core 17 fits the opening 18 relatively closely and may actually be press-fitted in the frame 19. Sheets 20 of zirconium are now applied to opposite faces of the assembled frame and fuel-element core. Now heat and pressure are applied to provide suitable bonds between the sheets 20 and the fuel-element core 17, the

sheets 20 and the frame 19, and'the fuel-element core 17 and the frame 19. Pressure is applied uniformly and simultaneously across the entire areas of the sheets 20 by a suitable pressure-welding unit. This may be done in a vacuum or anargon or helium atmosphere. The

assessiassembled sheets, fuelelement core, and frame are heated as rapidly as possible to some elevated temperature, for example, 1300F., and during this time, a pressure of somewhat less than .500 p.- s. i.is. applied. Thereaftera higher pressure, which may be 4000 p. s. i. for a fuela element core containing 4% uranitun, is applied until plastic deformation of the uranium-zirconium fuel-eles ment core 17 occurs, with the result that. the fuel-element core becomes bonded to the zirconium frame 1? and the zirconium sheets 20. Bonding of the frame to the sheets will also have occurred, since an appreciably lower pressure is required for plastic deformation of zirconium. If. a temperature higher than; l300F. is employed, the pressure required for plastic deformation of the. uraniumzirconium fuel element is less than 4000 p. s. i. When the desired amountof plastic deformation has occurred, the pressure is lowered just sufficiently to stop plastic deformation and maintainedat the lower value for about thirty minutes. Thereafter the temperature is lowered and thepressure is allowed to. drop to zero.

. The aforementioned heating to the elevated temperature which was given as 1300 F. should take place as rapidly as possible in order that any beneficial effects of recrystallization and grain growth may be obtained.

Although this is not essential for bonding, it is desirable that the surfaces of the fuel-element core 17, frame 19, and sheets 20 be cold-worked before the pres sure-welding process is carried out, in' order that recrystallization across the bonds may be facilitated.

In the modification shown in Figs. 7, 8, and 9, a uranium-zirconium fuel-element core 21, a zirconium frame 22, and zirconium sheets 23 are employed which correspond generally in composition to the fuel-element core 1'7,'the. frame 19, and sheets 20. of the modification of Figs. and 6, but the parts 21, 22, and 23 are bonded to one another by rolling rather; than by being simply pressure-welded to one another. The fuel-element core fits an opening 24 in the frame 22 and may actually be press-fitted therein. The frame 22 and sheets 23 have round corners 25, which fit round corners 26 in a steel frame 27 in which the fuel-element core 21, frame 22, and sheets 23 are positioned, the combined thickness of which isabout that of the steel frame. Steel sheets 28 are laid against the sheets 23 and the steel frame 27. The frame 27 and sheets 28 may be formed of a carbon steel having, for example, .18.23 %v carbon and other normal impurities. One face of thesteel frame against'which one steel sheet 28 rests has a recess 29. A hole. 30 extends from the recess 29 to an outer side of the. steel frame.

Thesteel sheets 28 and the steel frame 27 are. welded to one another, for example, by a metal-arc process, as indicated at 31, in order to constitute a box for thefuelelement core 21, the zirconium frame 22, and the. zirconium sheets 23,v which box may be. sealed off by applying a closure at the opening 30. Such .closure may take the formv of a tube 32 which is welded to the. steel frame 27 at the opening 30. The tightness. of. the welds 31 may be tested by immersion of. the steeLbox and. the contained partsin water and the applicationofa gas.- such. asiargon under pressure to the interior ofthe' box through thetubc 32. Ayacuum is now applied to the tube 32, and when the interior of the steel box is sufficiently evacuated, a region of the tube spaced-from the steel frame. 27 is heated, the tube is bent over on itself at thisregion, and the region is hammered flat until.sealed..

Now theparts are ready. to be. rolled.. This is carried? out in one or more passes through'rolls (not. shown): of the entire assembly composedt'o the. steel frame 27,.steeli sheets 23, zirconium-uranium fuel-elementicore 21, zirconium frame 22., and zirconium sheets23. Iris-"desirableto carry: out some appreciablev reduction. onthe: fuel. element andzirconium; frame and sheets; such as:3 to: 1. The rolling shouldbe performed at some suitable elevated: temperature" such as 1450 to 1650 F. Care:

must .be exercised-to .prevent bonding of the steel to the zirconium, and this requires a proper balance of elevated temperature and the amount of time at the elevated temperature used for the rolling. In other words, the more elevated the temperature, the less the permissible time at the temperature. The heating of the assembly may be done in air, since the zirconium and zirconium-uranium parts are sealedin a vacuum within the steel parts and thus are not subjected to oxidation or corrosion which might interfere with the formation of good bonds. The assembly is maintained for some time at the elevated temperature before each rolling pass. For example, if there are three passes, the assembly may be soaked or maintained at 1650 F. for thirty minutes before the first pass, reheated and soaked for fifteen minutes before the second pass, and reheated and soaked for ten minutes before the third pass.

After the assembly has cooled sufficiently, the steel sheets 28 and the steel frame 27 are stripped off. The round corners 25 on the zirconium frame 22 and the zirconium sheets 23 and the round corners 26 on the apertureinthe steel frame 27 have prevented these parts from diggin'g'into one another during the rolling process and thus facilitate removal of the steel frame. Now the zirconium-uranium fuel-element core 21 is located by means of radiography, and from this the thicknesses of the zirconium layer are determined. Then the jacketed fuel element is machined if necessary to bring the jacket to desired thickness.

The zirconium-uranium fuel-element core 21, the zirconium sheets 23, and the zirconium frame 22 may be formed from ingots that are hot-worked to desired dimensions. The hot-Working improves the bonding qualities andmay involve rolling in air at some elevated temperature such as 1450 F. after heating to this temperature in an argon atmosphere. The parts may be jacketed in steel or copper before being rolled. The parts to be rolled can also be formed by extrusion rather than castmg in ingots.

The one-piece zirconium frame 22 may be replaced by a split zirconium frame, shown in Fig. 10, composed of two parts 33 having oblique edges 34 in engagement with one another. It is simpler to manufacture the split frame than the two-part frame because of the ease of machining. The use of the split frame is feasible, because the steel frame 27 holds it together during the rolling of the entire assembly. The edges 34 of the parts 33 will become bonded to one another as a result of the rolling.

When thesteel plates 28 are being welded to the steel frame 27 as indicated at 31, the entire assembly may be clamped between water-cooled plates in order to be protected fromoverheating due to the welding. The welding maybe performed when the entire assembly is in an argon atmosphere.

An alternative processis to roll the assembled uraniumzirconium fuel-element core 21, the zirconium frame 22, and-the zirconium sheets 23'without encasing them in the steel frame'and steel-sheets; In this event the peripheries of the zirconium sheets are welded to' the zirconium frame-before the rolling by suitable means such as an argon-shielded tungsten-electrode are. This alternate process is specially adapted to a frame 22 and sheets 23 composed of about 5%- tin and the balance substantially zirconium. The small amount of tin im roves the cor-' rosion resistance of the zirconium with respect to water. Thus corroslon-resistant' welds of the above composition are obtainable in air by means of an argon-shielded a frame. and sheets of the jacket material will be applied about the core, and rolling or'pressure welding will be performed on the core and jacket to bond the jacket to the core.

While various embodiments of the instant invention have been presented, various modifications within the scope of the invention will be apparent to those skilled in the art. The invention is not limited by these embodiments but only by the claims which follow.

What is claimed is:

l. A process for enclosing a body of a first metal with a second metal, comprising inserting the body into an aperture in a frame of the second metal, placing a. sheet of the second metal on each of opposite sides of the assembled body and frame, and bonding the sheets to the body and the frame and the body and the frame to one another.

2. A process for enclosing a body of a first metal with a second metal, comprising inserting the body into an aperture in a frame of the second metal, the aperture generally fitting the body, placing a sheet of the second metal on each of opposite sides of the assembled body and frame, and applying heat and pressure to bond the sheets to the body and the frame and the body and the frame to one another.

3. A process for enclosing a body of an aluminumenn'ched-uranium alloy with aluminum, comprising inserting the body into an aluminum frame having an aperture substantially the same shape as the body, applying the legs of a U-shaped aluminum sheet against the opposite sides of the assembled body and frame, interlocking the free ends of said legs, and rolling the sheet, the body, and the frame to bond the sheet to the body and the frame and the body and the frame to one another.

4. The process specified in claim 3 and further comprising the steps of cutting off the interlocked free ends of the legs of the U-shaped sheet and the base thereof, applying a second U-shaped aluminum sheet against the portions of the first sheet now bonded to the frame and the body, interlocking the free ends of the legs of the second U-shaped sheet, and rolling to bond the second sheet to the said portions of the first sheet.

5. A process for enclosing a body of a zirconiumenriched uranium alloy in zirconium, comprising inserting the body into a zirconium frame having an aperture substantially the same shape as the body, placing zirconium sheets over opposite sides of the frame and body, and applying pressure simultaneously over the entire areas of the sheets to bond them to the frame and the body and the body and the frame to one another.

6. A process for enclosing a body of a zirconiumenriched uranium alloy in zirconium, comprising inserting the body in a zirconium frame, placing zirconium sheets on opposite sides of the frame and body in contact therewith, welding the sheets to the frame about the periphery thereof, and rolling the sheets, the frame, and the body to reduce them and to bond them to one another.

7. A process for enclosing a body of a zirconiumenriehed uranium alloy in zirconium, comprising inserting the body in a zirconium frame having round outer corners, placing zirconium sheets on opposite sides of the frame and body in contact therewith, applying a steel frame having round inner corners about the zirconium frame and steel sheets against the zirconium sheets, welding the steel frame to the steel sheets, rolling the entire assembly to reduce the body and the zirconium frame and sheets and bond them to one another, and stripping off the steel sheets and the steel frame.

8. The process specified in claim 7 and further comprising, prior to rolling, exhausting the space within the 'steel frame and steel sheets and sealing said space to produce better bonds between the body, the zirconium frame, and the zirconium sheets when they are reduced by rolling.

9. The process specified in claim 7, the steel frame being provided with a recess in one face contacted by one steel sheet and a hole leading from the recess to an outer side of the steel frame, the steel frame being further provided with a tube bonded to said hole and etxending externally of the steel frame, the steps prior to rolling of exhausting the space within the steel frame and the steel plates being carried out by the application of a vacuum to said tube, the step of sealing said space being carried out by the heating of a region of the tube spaced from the steel .frame and the bending over of the tube at said region to close the tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,374,110 Pittevil Apr. 5, 1921 1,886,615 Johnson Nov. 8, 1932 2,059,584 Johnson Nov. 3, 1936 2,064,684 Ostendorf Dec. 15, 1936 

1. A PROCESS FOR ENCLOSING A BODY OF A FIRST METAL WITH A SECOND METAL, COMPRISING INSERTING THE BODY INTO AN APERTURE IN A FRAME OF THE SECOND METAL, PLACING A SHEET OF THE SECOND METAL ON EACH OF OPPOSITE SIDES OF THE ASSEMBLED BODY AND FRAME, AND BONDING THE SHEETS TO THE BODY AND THE FRAME AND THE BODY AND THE FRAME TO ONE ANOTHER. 